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Author

First Name (or initial) / Middle Name (or initial) / Surname / Role (ASABE member, etc.) / E-mail / Contact author? yes or no
Morgan / D / Hayes / ASABE member / / yes

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Organization / Address / Country / Phone for contact author
USDA_ARS_USMARC / State Spur 18D, Clay Center, NE 68933 / USA / 610-393-7106

Author(repeat Author and Affiliation tables for each author)

First Name (or initial) / Middle Name (or initial) / Surname / Role (ASABE member, etc.) / E-mail / Contact author? yes or no
Tami / M / Brown-Brandl / ASABE member / / no

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USDA_ARS_USMARC / Clay Center, NE 68933 / USA
First Name (or initial) / Middle Name (or initial) / Surname / Role (ASABE member, etc.) / E-mail / Contact author? yes or no
John / P / Stinn / ASABE member / / no
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Iowa State University / Ames, IA 50010 / USA
First Name (or initial) / Middle Name (or initial) / Surname / Role (ASABE member, etc.) / E-mail / Contact author? yes or no
Hong / Li / ASABE member / / no
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University of Delaware / Newark, DE 19716 / USA
First Name (or initial) / Middle Name (or initial) / Surname / Role (ASABE member, etc.) / E-mail / Contact author? yes or no
Hongwei / Xin / ASABE member / / no
Organization / Address / Country / Phone for contact author
Iowa State University / Ames, IA 50010 / USA
First Name (or initial) / Middle Name (or initial) / Surname / Role (ASABE member, etc.) / E-mail / Contact author? yes or no
John / A / Nienaber / ASABE Member / / no
Organization / Address / Country / Phone for contact author
USDA_ARS_USMARC / Clay Center, NE 68933 / USA
First Name (or initial) / Middle Name (or initial) / Surname / Role (ASABE member, etc.) / E-mail / Contact author? yes or no
Timothy / A / Shepherd / ASABE Member / / no
Organization / Address / Country / Phone for contact author
Iowa State University / Ames, IA 50010 / USA

2013 ASABE Annual International Meeting PaperPage 1

2013 ASABE Annual International Meeting PaperPage 1

/ An ASABE Meeting Presentation
Paper Number: 131618005

House-Level Moisture Production of Modern Swine by Age, Temperature and Source

M.D. Hayes1, T.M. Brown-Brandl1, J.P. Stinn2, H. Li3, H. Xin2, J.A. Nienaber1, T.A. Shepherd2

1EMRU, USDA-ARS,MARC Clay Center, NE

2Agricultural and Biosystems Engineering, Iowa State University, Ames, IA

3Animal and Food Science, University of Delaware, Newark, DE

Written for presentation at the

2013 ASABE Annual International Meeting

Sponsored by ASABE

Kansas City,Missouri

July 21 – 24, 2013

Abstract.Minimum ventilation in swine housing is often used to control relative humidity in a barn. Thus, realistic data on latent heat or moisture production (MP) are critical to correctly determine the minimum ventilation needs. As part of a study to update heat production rates for modern swine genetics, latent heat production or MP has been calculated for various scenarios. The objective of this paper is to delineate MP by age of pigs, barn temperature and source which includes a) respiration of the pigs, b) evaporation of water from the manure pit and leaks in the waterers, c) combustion of fuel for supplemental heat of the barn, and d) evaporation of water from sprinklers systems. This will be obtained using MP data for pigs housed in indirect calorimetry chambers where moisture production sources other than the pig’s respiration are minimized, analyzing MP data for a full-scale empty barn with varying sprinkler usage or heater usage to determine MP unrelated to the pigs, and partitioning the whole-house MP according to the above sources for pigs of various ages and at different barn temperatures.

Keywords.latent heat, moisture production, swine, house-level moisture, relative humidity.

The authors are solely responsible for the content of this meeting presentation. The presentation does not necessarily reflect the official position of the American Society of Agricultural and Biological Engineers (ASABE), and its printing and distribution does not constitute an endorsement of views which may be expressed. Meeting presentations are not subject to the formal peer review process by ASABE editorial committees; therefore, they are not to be presented as refereed publications. Citation of this work should state that it is from an ASABE meeting paper. EXAMPLE: Author’s Last Name, Initials. 2014. Title of Presentation. ASABE Paper No. ---. St. Joseph, Mich.: ASABE. For information about securing permission to reprint or reproduce a meeting presentation, please contact ASABE at or 269-932-7004 (2950 Niles Road, St. Joseph, MI 49085-9659 USA).

INTRODUCTION

Raising pigs indoors requires a great deal of engineering and animal expertise. Many years of research have been dedicated to building design and environmental management, and improving the understanding of building and animal interactions. Intensive swine production requires a control system to manage environmental parameters. Ideally, the control system is designed for management of primary environmental variables like temperature, humidity and aerial contaminants. The environmental management is generally directed by adjusting ventilation rate (VR). Additional heating or cooling may be supplemented, but VR is the primary adjustment made. This desired VR varies based on local climate, barn design and management, and animal population and phase of production. In order to manage these parameters in the control system, the design values in the programming must reflect current animal and housing characteristics. In cold weather conditions, minimum VR is generally designed to manage humidity in a barn.

The relative humidity (RH) in a barn is based baseline moisture of incoming air,moisture added to the air in the barn, and the VR. Moisture enters the air through a number of channels. The animals produce water vapor by respiration, the animals also apply water to their skin and it evaporates off. Water evaporates from barn surfaces, like walls, floors, and the manure storage pit if the floor is slatted. As well supplemental heaters that combust propane or natural gas in unvented situations produce water vapor as a byproduct of the combustion. Recommendations are to keep RH under 80% (ASABE, 1986; Massabie et al., 1997). Higher RH levels result in mold and mildew growth (ASHRAE, 2010), increased bacterial growth and survivability (Wathes, 1983) as well as greater deterioration of the building and equipment due to condensation (ASABE, 1986). Massabie et al. also indicated a decrease in performance with RH greater than 80% (1997).

A variety of professional groups have provided design values (ASABE, 1986; ASHRAE, 2001). Bond et al. published moisture or latent heat production values, on which both ASABE and ASHRAE based recommendations (1959). Similar to total heat production moisture production values have changed since the studies due to changes in genetics, feed, and barn design and management (Brown-Brandl et al., 2004). There have been limited studies looking at latent heat or moisture production (MP) of swine. The studies have traditionally been completed in calorimetry chambers in studies also looking at total heat production, where moisture from sources other than the animals are minimized and temperatures are more precisely controlled. These values work well for total or sensible heat production design values, but as mentioned above, barn level MP is dependent on many other factors. From a review of literature a recent study did looked at barn level moisture production particularly a comparison of slatted and solid concrete floors (Christianson, 2003). Christianson’s study indicated design values did underestimate measured MP as well it indicated the factors for flooring type in the design values may not be accurate (2003).

The objective of this paper is to look at barn level MP values over months of intensive monitoring in a partially slatted barn. The barn was monitored both empty and with animals of varied production phases to determine normal operating parameters. The empty barn data was used along with recently collected calorimetry data to partition barn level values by source.

Materials and Methods

The study was conducted over 19 months in one growing/finishing facility and one wing of the farrowing facility at the US Meat Animal Research Center, Clay Center, NE to quantify facility-level HP and MP of swine and their surroundings from weaning to slaughter weight, and through late gestation, farrowing, and lactation (piglets were weaned between 20 – 27 days). Production phases, sex, and weight ranges, and herds used in the analyses are summarized in Table 1.

Table 1. Overview of Facility Level Experiments

Experiment / Sex / Weight Range (kg) / Weight Range (lb) / Groups Included in Analysis / Average Population
1. Nursery Piglets / Mixed / 10 – 20 / 22 – 44 / 2 / 513
2. Growing Pigs / Mixed / 20 – 40 / 44 – 88 / 2 / 416
3. Early Finishing Pigs / Mixed / 40 – 80 / 88 – 176 / 2 / 371
4. Late Finishing Pigs / Mixed / 80 – 130 / 176 – 286 / 1 / 295
5. Gestating Gilts / Gilts / 130 – 155 / 286 – 341 / 1 / 80

Site Description: nursery, finishing, and gestating

The facility measured 19.1 m  11.0 m (35 x 62.5 ft) with a capacity of approximately 500-200 pigs from 10-130 kg (22 -287 lb), respectively. The facility was divided into 16 pens (8 on the north wall and 8 on the south wall) used for the study and twowellness pens (i.e., for housing pigs needing special attention or treatment). The pens were partially slatted. The finishing facility had three exhaust fans, all on the east endwall (Figure 1), including two 0.76 m (30 in) fans, and one 0.6 m (24 in) fan. Air entered through the west endwall and was moved through a poly-tube (0.61 m, 24 in) to achieve more uniform distribution of air temperature across the pens. Two 73.25 kW (250,000 BTU/hr) unvented heaters were placed in the facility (one over each group of pens). Fluorescent lighting was used with 12 h light and 12 h dark. Herds were fed corn-soybean mash diets. Water was supplied through two nipple drinkers in each pen. The nipple drinkers as well as a sprinkler head were used over the slatted floor area of each pen. The sprinklers were used primarily to keep floor areas clean of defecation by running 45 seconds every 10 minutes (7.5% of the day).

Figure 1. Building layout and sampling sites for the nursery, growing, finishing and gestating gilt experiments. The overall building dimensions were 11 by 19.1 m (35 by 62.5 ft).

Measurement System

Concentrations of CO2 and dew-point temperature near the inlet and the exhaust fan were measured continually with CO2 and dew-point sensors (GMP222, Vaisala, Woburn, MA; DewTrakII, Edge Tech, Marlborough, MA). Concentrations of O2, CO2, and methane (CH4) were measured on a weekly basis. Samples were accumulated in Mylar bags that were analyzed at the end of the run. Heat production was calculated using indirect calorimetry methods (Nienaber and Maddy, 1985; Brown-Brandl et al., 2011). O2 and CO2 were measured within 100ppm. Respiration quotient (RQ) was calculated by dividing volume of CO2 produced by volume of O2 consumed.

All sampling pumps and valves, data acquisition, and instrumentation for this study were kept in an enclosure in the east end of the house. The enclosure was supplied with fresh air from outside to provide a positive pressure system in an effort to minimize entrance of dust from indoor air.

The building ventilation rate (VR) was determined from in-situ calibrated fan curves with 1.2 m (48 in.)fan assessment numeration systems (FANS) (Gates et al. 2004). Individual fan curves were established for each ventilation stage. The runtime of fans was recorded continuously with inductive current switches (Muhlbauer et al., 2011). Fan runtime along with the corresponding building static pressure (model 264, Setra, Boxborough, MA) were recorded every second. Using the calibrated curves for each fan stage with the above data, an overall building VR was calculated. All data were collected with a data acquisition system (NI-DAQmx, National Instruments, Austin, TX). To capture the dynamics of fan and heater operations, all data were processed on a per second basis.

Determination of facility-level MP and the relationship of MP and LHP

The facility-level MP, including latent heat of the pigs, evaporation from wet surfaces and heater combustion, was calculated from the following mass-balance equation:

MP = Q(Wo – Wa)(1) (1)

Where: MP = moisture production rate (g H2O s-1,lb H20 hr-1); Wo, Wa is humidity ratio of outlet and ambient air, respectively (g g-1, lb lb-1); Q is building ventilation rate (m3 s-1,ft3 hr-1);  = air density (g m-3, lb ft-3).

LHP = MP(hfg) (2)

Where: LHP = latent heat production (W, BTU hr-1); MP = moisture production rate (g H2O s-1,lb H20 hr-1); hfg = latent heat of vaporization (2429 J g-1, 1045 BTU lb-1)

In order to analyze facility-level production and quantify various sources of moisture generation, the facility was run in three scenarios: 1.) heat combustion; 2.) impact of sprinklers; and 3.) entire facility at full pig capacity.

In the first scenario, heater combustion rates were determined. This was done in an empty facility with a higher set point temperature and lower VR. This study provided an initial verification of the whole measurement system by verifying CO2 production and O2 consumption based on the amount of natural gas run through the gas meter (AL-800, Elster American, Nebraska City, NE). Based on stoichiometry, mass water vapor produced is related to the measured rate of natural gas combusted. This was done in order to gain an accurate MP rate for heaters independent of the facility.

In the second scenario, moisture generation was quantified while varying sprinkler runtime at two temperatures. The facility was again empty; however, the facility had not been cleaned from the previous study, to provide more realistic surface areas for evaporation. For this set-up, two indoor temperatures (17 and 20°C) were set and MP was measured. Heater runtime was determined and the related moisture produced was removed from the facility-level production rates. This provided valuable estimated evaporation rates from leaks, stuck nipple drinkers, and the pit as well as sprinklers. Because the sprinkling system was made on site, buckets were placed under six of the nozzles to capture the water volume. Although these are not precise specifications, this does provide some information on the rate of water flowing from the sprinkler system. Individual nozzles averaged 43±4.4 g H2O s-1 (341±4.4 lb H2O hr-1). Sprinkler runtime was varied at 0, 1, 3, 5, 7.5, or 10 minutes out of every 10-minute interval. Each test was run for at least 24 hours. After adjusting to the next setting, the facility was given at least 2 hours before the next sampling level. If the facility was stepping from a longer sprinkler runtime to a shorter runtime, sampling was held off until the following day to allow wet areas time to dry. One of the 7.5-minute tests did not successfully collect data for a full 24 hours and was, therefore, removed from the results.

In the third scenario, the facility was run with herds of pigs in either the nursery, growing or finishing phase. For this paper swine over 40 kg (88 lb) were considered finishing pigs and those between 20 and 40 kg (44–88 lb) were considered growing pigs and those pigs 10-20 kg (22–44 lb) were considered nursery piglets. During the course of the study five herds went through the facility. Although there were some inherent limits in temperatures based on seasons monitored, data from all production phases were sorted into four temperature range: 1) ≤ 21.1°C, 70°F; 2) 21.1 – 23.9°C, 70 – 75 °F; 3) 23.9 – 26.7°C, 75 - 80°F; 4) > 26.7°C, 80°F.

Animal LHP Equations From Calorimetry Studies

The following three equations were developed from calorimetry experiments as part of this larger project. These equations can be compared to barn-level MP values measured. Due to similarities in genetics, feeds and instrumentation of the pigs used in developing these equations and the ones grown and finished in this study, differences might be attributed to animal behaviors.

Nursery Pigs (10 – 20 kg):

LHP=- 2.26 + 0.194 ta + 0.0679 wt - 0.0034 tawt(3)

Growing Pigs (20 – 45 kg):

LHP=-1.64 + 0.173 ta + 0.021 wt - 0.0016 tawt(4)

Barrows (45 – 120 kg):

LHP=- 0.64 + 0.117 ta+ 0.0019 wt - 0.00054 tawt(5)

Gilts (45 – 120 kg):

LHP=- 0.46 + 0.077 ta + 0.0029 wt - 0.00032 tawt(6)

Where: LHP is latent heat production in W/kg, ta is ambient dry-bulb temperature in °C, and wt is live

body weight in kg.

RESULTS AND DISCUSSION

Supplemental Heater MP Verification

For this scenario, the barn was run for 24 hours. Based on the meter measurement of 896 ft3 of natural gas, and the one-second data of heater run time indicating the two heaters ran for a total of 240 minutes. This run time resulted in 3.37g CO2 being produced each second of heater run time. Through stoichiometry, the combustion relationship places the MP rate at 2.76 g H20 per second of heater run time. These values are quite reasonable indicating the heaters produced 244,700 BTU/hr, approximately 98% of the rated 250,000 BTU/hr.

Empty Facility MP Measurements

The objective in this scenario was to determine how much moisture was entering the air by evaporation from building surfaces. The amount of water supplied was adjusted by way of the sprinkling system. The sprinklers were on a ten-minute timer and percent of time running was adjusted.

Figure 2 below demonstrates the MP based on temperature. As expected, MP increases with increasing temperature. As well, more water being applied to the surfaces through sprinkler run time also resulted in increased MP to an extent. As the sprinkler run time increased above 50% the amount of MP leveled off. This indicates that for the RH, VR, and temperatures in this barn the maximum MP was achieved. The slight negative slope with temperature for the 100% sprinkler run time was initially confusing. However, the VR used to achieve these two conditions was similar. The differences here are most likely due to differences in incoming air as outdoor conditions included precipitation on one of the sampling days. This barn is typically run with sprinklers operating 7.5 to 10% of the time. For the purpose of partitioning MP the following equation (7) from the 10% sprinkler run time will be used.

MP = 0.18* ta – 1.47(7)

Where: MP is moisture production in g/s and ta is ambient dry-bulb temperature in °C

The empty facility measurements give us a strong indication of moisture from the pit and other drips/leaks. This facility is well maintained and was checked prior to starting the study, which limited water sources other than the pit. As well, when measurements were made with no sprinklers, the sampling did not start until the concrete appeared dry. Based on these measurements, this empty facility’s MP would range from 1.25 to 3.75 g/s over normal operating temperatures. The non-sprinkler run is between 70 and 100% of the normal operation of this barn (10% sprinkler run time)